Hello Alex,
As you know me from the sunvox forum, I am a pro user of sunvox, but I know almost nothing about pixilang. So, I want to ask you if with pixilang I could, in some way, make small movies (shorter than 5 minutes), because I like more programing environment, than unprecise manipulations through a gui. What exactly I need is to :

- crop a piece of film (made with a phone) ;
- mute its sound and add a different .wav sound
- insert at the begining and at the end some short video (with audio) sequences
- superpose in a corner a small .png which has some transparent parts
- render the whole video result in a web compatible format

In the current version there is no simple cross-platform way to load MP4 (or other video) files.
Pixilang can only load animated GIFs or set of JPEGs / PNGs.
But. If you are the Linux user, try to use these examples (attached) which are based on the ffmpeg_video_export and ffmpeg_video_import libraries.
It uses the ffmpeg (command line tool) for decoding and encoding video stream.